Centrifugal separator



CAl -GRgNl INILSON 7' 3,499,602

March 10, 1970 mf i bag SEiARATOR Filed April 24; 1968 C041. 40mm 014x00 INVENTOR I M X/yw, 7'

United States Patent US. Cl. 233-21 7 Claims ABSTRACT OF THE DISCLOSURE Within the centrifugal rotor is a conveyor screw arranged for continuously discharging sludge separated from a liquid supplied to the rotor, the conveyor screw defining with the rotor at least two side-by-side helically extending channels within the rotor. One of these channels communicates with the rotor inlet for liquid to be separated, and another communicates with the liquid outlet of the rotor, these two channels being so interconnected that liquid supplied to the rotor, in passing from the inlet to the liquid outlet, is caused to flow through the two channels one after the other while being separated.

The present invention relates to centrifugal separators of the type comprising a rotor and a conveyor screw arranged therein for the discharge of sludge, or the like, separated from a liquid supplied to the rotor.

The rotor of a centrifugal separator of this type generally comprises a cylindrical section and, connected thereto, a conical section tapering in the feed direction of the conveyor screw. For the supply of liquid to be separated within the rotor, the separator has a pipe or the like which generally opens into the conical section of the rotor. The cylindrical section of the rotor terminates in an end wall having a number of outlets for liquid which has been freed from sludge. These outlets in the end wall of the rotor determine the position of a cylindrical liquid surface formed within the rotor and extending axially from the end wall to a place in the conical section of the rotor.

The conveyor screw within the rotor is arranged to be driven at a speed slightly different from the speed at which the rotor is driven, so that sludge settled-at the circumferential wall of the rotor during the separation is fed by the conveyor screw axially, from the cylindrical section of the rotor through the conical section of the same to an outlet at the narrowest end of the conical section.

The present invention provides a centrifugal separator of the type described above, which has a considerably higher separating efliciency than previously known separators of this type.

In the centrifugal separator according to the invention, the rotor does not necessarily have a conical section but may be entirely cylindrical. The separator is characterized in that the conveyor screw forms with the rotor at least two side-by-side channels therein which extend helically about the rotor axis, of which channels one communicates with the rotor inlet for liquid to be separated, and one communicates with the liquid outlet of the rotor, the channels being interconnected in series so that liquid supplied to the rotor, on its way from the inlet to the liquid outlet, is caused to flow through the different channels, one after the other, while being separated.

In some instances it may be suitable to divide one or more of these channels longitudinally into two or more passages, or to provide the channels with different crosssectional areas, or both.

In a preferred embodiment of the invention the helically extending sludge-actuating members of the conveyor screw are formed so that at least one of such channels is confined by these members and the rotor radially outside the liquid surface formed within the rotor during the centrifugal separation. In such cases, when this channel extends radially outside said liquid surface along the whole of itslength, special means are required for the connection of such channel with the rotor inlet for liquid to be separated, which means are arranged to rotate with the conveyor screw.

One embodiment of the invention is described in detail below with reference to the accompanying drawing, in which the single illustration is a schematic view in axial section of a centrifugal separator constructed according to the invention.

I The centrifuge as illustrated comprises generallly a rotor 1 mounted by conventional means (not shown) for rotation about a horizontal central axis, a conveyor screw 2 mounted in the' rotor for rotation relative thereto about the rotor axis, and means 3 for supplying sludgecontaining liquid to the rotor.

The rotor 1 comprises a cylindrical section 4 and, connected thereto, a conical section 5 tapering in the feed direction of the conveyor screw 2. The cylindrical section 4 is terminated by an end wall 6 having a number of outlets 7 for liquid supplied to the rotor and which has been freed from sludge or the like by centrifugal separation. The liquid discharging through the outlets 7 is illustrated by arrows 8. The outlets 7 determine the radial position of a cylindrical liquid surface Swhich is formed within the rotor and extends axially from the end wall 6 to a place in the conical rotor section 5.

For the sake of clarity, only the sludge-actuating member of the conveyor screw 2 is shown, which extends helically around the rotor axis and through the cylindrical as well as the conical section of the rotor, as can be seen from the drawing. The conveyor screw 2 is arranged to feed sludge, settled within the rotor, from the cylindrical rotor section 4 to a number of sludge outlets situated in the narrow end of the conical rotor section 5 and shown collectively at 14. Sludge discharging through outlet 14 is illustrated by arrows 9.

Part of the helically extending sludge-actuating member 2 of the conveyor screw is formed with a radially outward opening profile 2a of generally U-shaped crosssection. This part extends from the end wall 6 along the cylindricalrotor wall 4 to the conical rotor section 5. In the concial section of the rotor, the length of the front leg of the U-profile, reckoned in the feed direction of the conveyor screw, is gradually decreasing and is no longer existing at the portion of the circumferential rotor wall situated radially inside the liquid surface S formed within the rotor. In the region of this portion of the circumferential rotor wall, the conveyor screw 2 has the same form as a conventional conveyor screw for this purpose.

In the illustrated embodiment, the means 3 for supplying liquid to the rotor 1 consists of a first pipe 10 extending axially into the rotor, and a second pipe 11 communicating with the pipe 10 and firmly connected to the conveyor screw 2 so that it rotates with the latter. The pipe 11 opens into a helical channel 12 defined by the rotor wall and the U-profile 2a of the sludge-actuating member 2 of the conveyor screw. The channel 12 extends helically along the cylindrical circumferential wall 4 of the rotor from the end wall 6 to the conical rotor section 5, where the U-profile gradually changes in the manner described above.

As illustrated, the helically extending sludge-actuating member 2 of the conveyor screw is situated entirely radially outside the liquid surface S in substantially the whole liquid-containing part of the rotor 1. Thus, only such means (not shown) necessary for driving and centering the helically extending member 2 breaks through the liquid surface S.

---In--the operation of the illustrated centrifuge, liquid to be separated is supplied to the rotor 1 through the pipes and 11. From the pipe 11 the liquid is led into the channel v12 which is closed by a sludge layer settled on the cylindrical rotor wall, which layer cannot be reached by the conveyor screw 2. Within the channel 12, the liquid is led to the conical section 5 of the rotor while being subjected to a first separating operation. During this first separating operation a portion of the sludge contained by the liquid settles out, this portion forming a bank in front of the rear leg of the U-profile 2a of the sludge-actuating member (reckoned in the feed direction of the conveyor screw).

-When the liquid reaches the conical rotor section 5, one leg (in this case the front leg) of the U-profile 2a gradually tapers off until it is eliminated, so that the helical channel 12 gradually opens and disappears. Then the sludge already separated from the liquid is fed further by the conveyor screw to the sludge outlet 14, while the liquid is-caused to flow to the outlets 7 in the end wall 6 of the rotor by way of another helical channel 13 separated from the channel 12.

In flowing through the second helical channel 13, the liquid is subjected to a second separating operation which, due to the shape of the conveyor screw 2, does not disturb and is not disturbed by the aforesaid first separating operation, to which new liquid is continually being subjected. Sludge settled out during the second separating operation forms a bank in front of the front leg of the U-profile 2a, which bank .joins the previously mentioned bank (formed in front of the rear leg of the U-profile) in the conical section 5 of the rotor and is then transported further by the conveyor screw to the sludge outlet 14.

A liquid supplied to the rotor of a centrifugal separator, constructed as described above, is subjected to a most effective separation. Due to the special shape of the means 3 for the supply of feed to the rotor and the special shape of the conveyor screw 2, the liquid is caused to flow twice through the rotor while subjected to the largest possible centrifugal force. Also, the separation may continue undisturbed at all times, due to the fact that no turbulence arises when new liquid is supplied to the rotor.

The illustrated centrifugal separator is only one embodiment of the present invention, other embodiments being possible without departure from the inventive idea. For example, a centrifugal separator according to the invention, instead of having a conveyor screw formed as described above, may have a conventional double-threaded conveyor screw, the helically extending sludge-actuating members of which define together with the rotor two sideby-side helically extending channels communicating with each other and with the inlet and liquid outlet, respectively, of the rotor as previously described.

If'the centrifugal separator is equipped with such a conventionally formed double-threaded conveyor screw, the sludge-actuating members do not necessarily have to be formed so that they, together with the rotor, define one channel situated entirely radially outside the liquid surface S in the rotor. Preferably, each space between the two threads of the conveyor screw forms a channel which, during the operation of the separator, only partly (i.e., the radially outermost part) contains liquid to be separated.

When separated. in a centrifugal separator comprising a conventionally formed double-threaded conveyor screw, all the liquid supplied to the rotor is forced to follow the helically extending sludge-actuating members of the conveyor screw on its way from the inlet pipe 11 to the liquid outlet 7 in the end wall of the rotor, in the longitudinal direction of the channels (corresponding to said channels 12, 13)- defined by the sludge-actuating members. As can be seen from the drawing showing the previously described embodiment of the invention, a portion of the liquid to be separated is allowed to fiow transversely in relation to he one channe ie, the ch nn l 13.

- The necessary-connection between thedifferent channels may be arranged in any suitable manner, as by perforations through the sludge-actuating members or simply by the omission of these members at suitable places. Further, the channel communicating with the rotor inlet may be closed in one direction, in any suitable way, in order to assure that the liquid supplied to the same flows in the right direction.

Within the scope of the inventive idea, it is also possible to lead liquid to be separated through three or more channels defined by the conveyor screw and the rotor, which channels communicate with each other and with the rotor inlet and outlet as previously described. If there are more than two channels, certain obvious measures must be taken in order to prevent the channel or channels first passed through by the liquid from being entirely filled with sludge.

I claim:

1. In combination with a centrifugal rotor having an inlet for sludge-containing liquid, the rotor also having a sludge outlet and an outlet for liquid separated from the sludge, a conveyor screw mounted in the rotor for con.- tinuously discharging separated sludge through said sludge outlet and defining with the rotor two side-by-side channels extending helically about the rotor axis, one of said channels communicating with said rotor inlet, the other channel communicating with said liquid outlet, said helical channels being interconnected in series whereby liquid supplied to the rotor, in passing from said inlet to said liquid outlet, is caused to flow through the two channels one after the other and in opposite directions, respectively, while being separated from sludge.

2. The combination according to claim 1, in which said one channel has a smaller cross-sectional area than said other channel.

3. The combination according to claim 1, in which said liquid outlet determines the radial position of the free liquid surfaceformed in'the rotor during the centrifugal separation, one of said helical channels being defined radially outside said liquid surface;

4. The combination according to claim 3, comprising also means rotatable with the conveyor screw for conmeeting said rotor inlet with said channel defined radially outside said liquid surface.

5. The combination according to claim 1, in which said liquid outlet determines the-radial position of the free liquid surface formed in the rotor during the centrifugal separation, one of said helical channels being defined radially outside said liquid surface, the'conveyor screw including sludge-actuating members extending helically throughout substantially the whole liquid-containing part of therotor and located entirely radially outside said liquid surface. I

6. The combination according to claim 1, in which said sludge outletand said liquid'outlet are at opposite ends, respectively, of the rotor, said rotor inlet communicating with said one channel at part of the rotor near said liquid outlet, said channelscornmunicating with each other at a location between said part and the sludge outlet.

7. The combination according to claim 6, in which the rotor has a substantially cylindrical section and a section tapering from the cylindrical section in the feed direction of the conveyor screw, said channels communicating with each other in said tapering section.

References Cited UNITED STATES PATENTS a ROBERT W. JENKINS, Primary Examiner 

